1. Field of the Invention
The present invention relates to a method and an apparatus for signal transmission in a CDMA (Code Division Multiple Access) mobile communication system in which base stations and a mobile station carry out communications according to the CDMA scheme by transmitting transmission signals which are formed by control signals or user signals through a radio channel set up between each base station and a mobile station.
2. Description of the Background Art
Here, a conventional signal transmission method for a mobile communication system will be described by taking an example of a radio channel set up before the start of a communication between a base station and a mobile station in a digital mobile communication system called GSM which is currently used for the mobile communication service mainly in Europe.
In the GSM, a plurality of transmission signals are transmitted between a mobile station and a base station through a radio channel which is set up between the mobile station and the base station before the start of a communication. The transmission signal processing time required at each of the base station and the mobile station reaches as much as several hundred msec., and no transmission signals are transmitted on the radio channel during that processing time. However, in the conventional mobile communication system (GSM), the radio channel has been always continuously transmitted regardless of the presence or absence of transmission signals to be transmitted.
Now, in the CDMA mobile communication system, the system capacity is determined by an amount of interference power, and the system capacity decreases as an amount of interference power increases. In order to prevent an increase of an amount of interference power, there is a need to eliminate wasteful radio channel transmission.
However, even in the conventional CDMA mobile communication system, when the transmission signals are to be transmitted through the radio channel between a base station and a mobile station, the radio channel has been always continuously transmitted regardless of the presence or absence of transmission signals to be transmitted, so that an amount of interference power has been increased unnecessarily and the system capacity has been decreased unnecessarily.